Method and system for creating a textured surface on an implantable medical device

Abstract

A method for forming an implantable medical device, such as a stent, is provided, in which electric discharges are applied to a metal surface of the implantable medical device. The electric discharges pit the surface. The pitted surface improves retention of a coating on the device and increases the amount of coating that can be carried by the device. An electric discharge machining process is described for applying electric discharges to the surface of the implantable medical device or portion thereof.

Description

CROSS REFERENCE[0001]This is a divisional application of U.S. Ser. No. 09 / 752,497, which was filed on Dec. 27, 2000 now U.S. Pat. No. 6,913,617.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates generally to methods for forming surface features of implantable medical devices. More particularly, the present invention is directed to methods of using electric discharges to roughen the surface of implantable medical devices, such as stents and grafts, with numerous pits.[0004]2. Description of the Background[0005]Percutaneous transluminal coronary angioplasty (PTCA) is a procedure for treating heart disease. A catheter assembly having a balloon portion is introduced into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predeterm...

AI Technical Summary

Benefits of technology

[0013]An implantable medical device capable of delivering therapeutic substances from a coating is provided, along with a method of preparing the device. In comparison to a conventional implantable medical device, the implantable medical device of the present invention can better retain a coating and allow a greater total amount of coating to be carried by the device, thereby allowing for greater amounts of therapeutic substances to be delivered from the device.

[0015]In various embodiments, the pitted region of the surface, or a portion thereof, can be coated with a coating containing a therapeutic substance or substances, a polymer, or a combination of therapeutic substances and polymer. The coating can be made of one or more layers and the various layers can include different therapeutic substances, polymers, or combinations of therapeutic substances and polymers. The pitted surface has a greater surface area than a smooth surface, allowing for more coating to adhere to the surface, and provides a better mechanical hold for the coating, thereby improving coating retention.

Problems solved by technology

Following the PTCA procedure, however, damage to the arterial lining can potentially cause re-occlusion of the artery, due to thrombosis, restenosis, or collapse of the arterial walls.

An obstacle often encountered with the use of stent coatings is poor adhesion of the polymeric coating to the surface of a stent.

Also, when a coated stent is expanded in situ, the distortion the stent undergoes as it expands can cause the coating to peel, crack, or tear, and disengage from the stent.

Poor adhesion of the coating material can promote thrombosis and restenosis, by providing additional surfaces for platelets and other blood components to adhere.

Additionally, poor adhesion and loss of the coating also leads to loss of a significant amount of the drugs to be delivered from the coating.

Another technical challenge in using stent coatings to deliver drugs is loading enough drug onto the stent, so that an effective amount of the drug or drug combination is delivered to the treatment site.

However, increasing the thickness of a stent coating can be difficult, particularly if the coating does not adhere well to the stent material.

When the electric discharges strike the surface of the implantable medical device, material that forms the surface of the device vaporizes, leaving pits or voids, which cause the surface to be rough.

The resulting arcs pit the surface of the device.

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